Drip irrigation system problem

I have a 4 zone drip system. As the system runs, I adjust all of the drippers. Then shut off the system for 15-20 minutes. When I restart some of the drippers do not have enough pressure If I manually open the dripper slightly (loosen/unscrew) pressure comes right away with some spitting and popping (I assume the system is bleeding itself).

I've replaced all of the drippers just to take that out of the equation.

Adjustable Shrubbler type emitters? Sounds like it..the kind you can open and close and anything in between?

They tend to "adjust" themselves if you know what I mean.....even the "flag" type emitters will do this sometimes......I recommend switching to a pressure compensating type emitter...this type of emitter will NORMALLY not have this problem, level ground or unlevel ground.....

I am guessing here, but it is about all I have got so far. I would guess that since they are all installed on the ground level, they are draining when the system is turned off. When the system is turned back on, the water / air rushes through and causes the adjustable emitters to self adjust themselves / or give a spitting sound or effect. This can give the the false since on the emitters not having adequate pressure / or flow. I would suggest pressure regulation on all of your low volume / drip lines, and allow adequate time for the system to stabilize before checking it again (turn on and let run for about 10-15 mins). Most low volume systems are just that, real low volume, and they need more time to deliver unlike their standard irrigation counterparts. Its a stretch and its a guess!